Ultrasound from a focused ultrasonic transducer can be used to selectively treat regions inside a subject. Ultrasonic waves are transmitted as high energy mechanical vibrations. These vibrations induce tissue heating as they are damped, and they can also lead to cavitation. Both tissue heating and cavitation can be used to destroy tissue in a clinical setting. However, heating tissue with ultrasound is easier to control than cavitation. Ultrasonic treatments can be used to ablate tissue and to destroy regions of cancer cells selectively. This technique has been applied to the treatment of uterine fibroids, and has reduced the need for hysterectomy procedures. At lower powers or in pulsed mode, ultrasound can be used to selectively deliver genetic material or medicine to a region.
To perform ultrasonic therapy, a focused ultrasonic transducer can be used to focus the ultrasound on a particular treatment volume. The transducer is typically mounted within a medium, such as degassed water, that is able to transmit ultrasound. Actuators are then used to adjust the position of the ultrasonic transducer and thereby adjust the tissue region that is being treated.
HIFU procedures in a clinical setting are typically image-guided to permit treatment planning and targeting before applying a therapeutic or ablative level of ultrasound energy. Usually MRI is used for image-guidance, but it is also possible to use ultrasonography.
United States patent application US 2011/0313329 defines a therapy system for depositing energy which has a feed forward control of the therapy module. Particularly, in this known therapy module the cooling down period is estimated on an a priori estimate on the induced heating.